1. Field of the Invention
The present invention relates to an electrophotographic photoconductor, and more specifically, an electrophotographic photoconductor having an improved base drum.
2. Background of the Related Art
Conventionally, a base drum of an electrophotographic photoconductor is prepared by forming an aluminum drum by extrusion and machining the surface of this aluminum drum to obtain a mirror surface. This is because the base drum of the electrophotographic photoconductor is required to have high dimensional accuracy and excellent surface smoothness. However, this method of preparing the base drum of the electrophotographic photoconductor has the shortcomings that the manufacturing cost is considerably high and the drum must be thick enough to withstand the surface fabrication process.
Base drums prepared by a drawing and ironing process which do not need extensive fabrication have been proposed in the process disclosed in, for example, Japanese Laid-Open Patent Applications Nos 58-202454, 59-10950, 59-200249 and 61-65256. This process makes it possible to form a thin-walled drum without any necessity of surface machining or other such fabrication. However, this process has the shortcoming that the length of the drum is restricted when the predetermined diameter of the drum is small, although a long drum can be formed when the diameter thereof is increased. More specifically, the length of the drum can be no more than about 3 to 5 times the diameter thereof. The electrophotographic photoconductor is generally required to have a length of 210 mm or more from the viewpoint of its function. To form a 210 mm-long base drum by following the drawing and ironing process, the diameter thereof exceeds at least 40 mm. Therefore it is very difficult to form a 210 mm-long base drum of the electrophotographic photoconductor with a diameter of less than 40 mm by the drawing and ironing process. In addition, the base drum cannot be continuously manufactured by this process, which results in poor productivity.
Metallic drums which are prepared by impact extrusion have been proposed in Japanese Laid-Open Patent Application No. 57-115560. This method has also the shortcomings that the productivity is poor because the metallic drums cannot be continuously manufactured due to batch production, and that the diameter and length of the drum are restricted when the thickness thereof is decreased.